1. Field of the Invention
The present invention relates to container securement devices and more particularly to improvements in cargo container securement devices providing automatic securement and release of a cargo container.
2. Discussion of Prior Art
Containerized lading has become immensely popular due to advantages such as labor savings resulting from decreased cargo handling. Modular or standardized containers may be shipped from point to point using a variety of different carriers including rail cars, trucks and ships. Such cargo containers are conventionally provided with corner castings including locking openings used in securing the containers to the various types of vehicles upon which they are loaded.
One type of container securement device used in the past is a container pedestal including a base portion upon which a corner of the container rests, as well as vertically extending walls within which a corner of the container is captured. A latch pivotable about a horizontal axis engages a locking opening in a vertical wall of the container for holding the container down against the base while permitting automatic entry and release of the container. One example of such a container pedestal is disclosed in U.S. Pat. No. 4,382,734.
Another securement device used in the past with cargo containers is a twistlock. This device includes a base upon which the container may rest together with a shear block engageable with a locking opening in the bottom, horizontal wall of the container corner casting. A locking head is manually moved from a released position in alignment with the shear block to a locked position in which the container cannot be lifted away from the base. The head is rotated manually between the locked and the unlocked positions, and automatic entry and release of the container is not possible.
The primary use of container pedestals has been on rail cars where containers are typically loaded and unloaded with a crane and automatic entry and release are important. On the other hand, twistlocks have primarily been used to secure containers to trucks where their small size and light weight is an advantage.
U.S. Pat. No. 4,626,155 ('155 patent), which issued to Hlinsky, et al., discloses an automatic container securement device with a spring biased, cam surfaced head. The '55 patent teaches a device for automatically securing a cargo container to a support such as a deck of a vehicle or a second container with which the first container is to be stacked. The device includes a base having a projecting shear block received in the locking opening of the container. A head rotates between an unlocked or loading position in which the head moves through the locking opening and a locked position in which the container is secured. Automatic entry and release are provided by a spring within the base biasing the head to the locked position but permitting movement to the unlocked position when torque is applied by engagement of the container with a cam surface on the head. Visible indication of the locked position and positive locking of the head in the locked position may be provided. For stacked containers, two aligned shear blocks and two angularly offset heads are provided and the spring may be released for manual locking of the device to one container followed by automatic locking to the second container.
It will be seen from a further review of the above-referenced patents and other prior art generally known to exist that the prior art does not teach an automatic twist lock device comprising a uniquely configured shaft member for receiving springs of varying types, which various springs may be interchanged with one another depending on the requirements of the target location. Further, it will be seen that the prior art does not teach the use of spiral torsional springs constructed from tempered steel for effecting substantially uniform spring performance across a wide range of temperatures. The prior art thus perceives a need for an automatic twist lock device comprising a uniquely configured shaft member for receiving and actuating springs of varying types, which various springs may be interchanged with one another depending on the requirements of the target location. Moreover, the prior art perceives a need for an automatic twist lock incorporating a spiral torsional spring constructed from tempered steel for effecting substantially uniform spring performance across a wide range of temperatures.